Preform for manufacturing a material having a plurality of voids and method of making the same

ABSTRACT

A beaded preform includes a plurality of adjacently positioned beads for forming a plurality of voids in an engineered material. The beaded preforms may be comprised of a filaments (single strand of beads) and mats (two-dimensional and three dimensional arrays of beads). The filaments and mats may be coated to become tows and laminates, respectively, which may then be assembled into composite materials. The preforms may be produced using novel manufacturing apparatuses and methods, and incorporated into known manufacturing processes to produce porous structures, including stress-steering structures, in any material including metals, plastics, ceramics, textiles, papers, and biological materials, for example.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/860,349 filed on May 17, 2001, now U.S. Pat. No. 6,767,619, theentire disclosures of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the design and manufacture ofmaterials, and more particularly to a preform component used to generatevoids, pores, or cavities in any material especially engineeredmaterials.

2. Background of the Related Art

This invention relates in general to the ability to establish aplurality of organized voids in a material, and also to load bearingstructures and structures that provide an enhanced trade-off between thestress that can be safely carried in relation to the amount of materialrequired for the structure.

Generally, voids have been created in materials using a number ofexisting foaming techniques. These foaming techniques produce materialshaving voids which are unorganized; i.e., the voids are randomlypositioned as well as randomly placed. Moreover, a number of the voidsin these materials are not enclosed—they are interconnected withadjacent voids.

Accordingly, existing processes cannot produce materials having enclosedvoids and/or voids in a truly organized position within a material.Current techniques will also not allow voids to be created to an exactpredetermined size and shape which are substantially self-enclosed.

Having voids which are organized non-interconnected voids is especiallyimportant in stress steering materials. Stress steering materials allowfor forces placed on a structure to be resolved largely into compressiveforces.

Such stress steering materials having symmetrically arranged voids havebeen developed which resolve a substantial majority of the stressesplaced on the material into compressive stress using a novel structurecontaining voids. Such novel structures are disclosed in U.S. Pat. Nos.5,615,528, 5,660,003, and 5,816,009, the disclosures of which areincorporated herein by reference (each patent being owned in common withthe present application). Each of these disclosures describes the use ofa plurality of uniform, symmetrically arrayed voids throughout the basematerial which results in a material structure that resolves the forcesimposed thereon largely into compressive rather than tensile stress.

Research by NASA, and other respected scientific organizations, hasdetermined that the more nearly uniform the voids and the more nearlysymmetrical the arrangement of voids in a material, the greater theeffective tensile strength of the material. Consequently, makers offoamed materials, and other materials in which porosity is a factor,have long sought a commercial method for positioning pores, or voids, ofa predetermined size(s) in predetermined locations in a material to givethe material a precise, three-dimensional morphology in order tooptimize its effective tensile strength.

However, incorporating these voids in a three-dimensional symmetricalarrangement in materials is at best an arduous and costly task usingconventional manufacturing techniques. Indeed, this is not yet possiblewith known material foaming techniques. Hence, the widespread use andacceptance of porous materials, including the stress steering materialsdisclosed in the above-identified patents, have been hampered due to thedifficulties of incorporating the essential voids in materials.

Accordingly, there exists a need for a material, process, and/or systemthat will allow for easy manufacture of materials with predeterminedmorphologies that incorporate voids, including the patented stresssteering materials.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides methods and apparatuses forcreating organized vorasity (voids positioned in a predeterminedarrangement) in any material. The voids created using these novelmethods and apparatus may be of any size, shape, and spacing, and mayalso be interconnected or each may be entirely enclosed.

Moreover, the spacing of the voids in a particular material may besymmetrical and/or asymmetrical to attain a desired materialcharacteristic. Thus, to attain stress-steering according to thematerials disclosed in the aforementioned patents, the voids must bearranged in a particular symmetrical arrangement.

Accordingly, materials with predetermined morphologies that incorporatevoids, including the patented stress-steering materials that utilize aplurality of symmetrically arrayed, uniform voids to resolve forcesimposed on a structure primarily into a compressive rather than tensilestress, may be manufactured using the unique and novel components andmethods according to the present invention.

The preforms, examples of voided structures, as well as themanufacturing apparatuses and methods according to the present inventionare also disclosed in a corresponding provisional application, filedconcurrently with the present application by the same applicant andcommonly owned with the present application, entitled, “Preform ForManufacturing A Material Having A Plurality of Voids And Method OfMaking The Same”, filed by Express Mail, Label No. EK715814181US, with adate of deposit of May 17, 2001, the entire disclosure of which isincorporated herein by reference.

In preferred embodiments of the present invention, voids areincorporated into-a material through the use of either a preformmaterial component or texturizing, or a combination of the two. Thevoids may be created in a material using known manufacturing methods.

Thus, it is an object of this invention to provide a component materialfor establishing a plurality of voids.

It is another object of the present invention to provide a method ofimparting a plurality of voids into a material.

Accordingly, in one aspect of the present invention, a beaded preformfor forming a plurality of voids in an engineered material includes aplurality of adjacently positioned beads.

In another aspect of the present invention, a method for manufacturing abeaded preform for forming a plurality of voids in an engineeredmaterial includes extruding a preform material out a first opening toproduce an extruded preform material and calendering the extrudedpreform material to form a plurality of adjacently positioned beadsthereon.

In yet another aspect of the present invention, a method formanufacturing a coated, beaded preform for forming a plurality of voidsin an engineered material includes providing a first flow of anextruding coating material to die, providing a beaded preform within thefirst flow, where the beaded preform is coated with the coatingmaterial, and extruding the first flow with the beaded preform from anopening to form a tow.

In yet another aspect of the present invention, a method for producingan engineered material having a plurality of voids includes guiding aplurality of beaded preforms into a supply of a first material, coatingthe plurality of beaded preforms with the first material, shaping thecoated preforms into a predetermined form and consolidating the form.

In yet another aspect of the present invention, a method for producingan engineered structure comprised of a plurality of organized voidsusing a continuous casting apparatus includes guiding a beaded preformcomprising a plurality of adjacently positioned beads into a matrixmaterial, the material matrix held in a first container, guiding thematrix material into a space having a predetermined distance, whereby aproduct is formed having a predetermined thickness substantially equalto the distance.

In yet another aspect of the present invention, a method for forming acomposite having a plurality of organized voids arranged thereinincludes imparting a first array of first voids upon a first laminate,whereby openings to the first voids are formed on a first side of thefirst laminate, and assembling the first laminate with a secondlaminate.

In yet another aspect of the present invention, a laminate for assemblyinto a composite material includes a texture comprising a plurality ofrecesses on a first side, where the recesses correspond to a pluralityof projections on a second side of the laminate.

In yet another aspect of the present invention, a method ofmanufacturing an engineered material having a plurality of organizedvoids includes guiding a beaded preform comprising a plurality of spacedapart beads within a continuous cast of molten material.

In yet another aspect of the present, a method of manufacturing anengineered material having a plurality of organized voids includesproviding a beaded preform comprising a strand of adjacently positionedbeads into any one of the following manufacturing processes:

-   -   additive manufacturing, atomistic manufacturing, layered        manufacturing including fused deposition modeling,        stereo-lithography, optical fabrication, solid base (ground)        curing, plasma spray forming, sputtering, vapor deposition,    -   deformation and forming including bulk deformation processes        including impression-die forging, open-die forging, coining,        piercing, hubbing, fullering and edging, roll forging, ring        rolling, direct extrusion, indirect extrusion, hydrostatic        extrusion and impact extrusion,    -   sheet metal forming processes including shearing, bulging,        rubber forming, high-energy-rate forming, superplastic forming,        deep drawing, embossing,    -   material removal including cutting, grinding, electrical        discharge machining, water-jet machining, abrasive-jet        machining, chemical machining and electrochemical machining and        grinding,    -   casting including permanent molds including slush casting,        pressure casting, insert molding, centrifugal casting and        infiltration casting expendable molds including vacuum casting,        ceramic-mold casting, plaster-mold casting, shell-mold casting        and sand casting, gel-casting, injection molding, compression        molding, transfer molding, insert molding,    -   particulate material processing including sintering, cold        isostatic pressing, and hot isostatic pressing, and    -   assembly and joining processes including friction stir welding,        Resistance welding, explosive welding, brazing and soldering,        arc welding, and laser welding.

These aspects will be better understood with reference to theaccompanying drawings and the below detailed written description of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first, closed cell architecture of a stresssteering structure created by preforms according to the presentinvention, in which all of the figurative TRDs have a void at theirrespective centers.

FIG. 2 illustrates a second, open-cell architecture of a stress steeringstructure created by preforms according to the present invention, inwhich every other figurative TRD is removed.

FIG. 3 illustrates a third, combination, open-cell, closed cellarchitecture of a stress steering structure created by preformsaccording to the present invention, in which figureative TRDs have avoid at their respective centers.

FIG. 4 illustrates a fourth, combination, open-cell, closed cellarchitecture of a stress steering structure created by preformsaccording to the present invention, in which figureative TRDs have avoid at their respective centers.

FIG. 5A illustrates a string of pearls which resemble a preformaccording to the present invention.

FIG. 5B illustrates a schematic view of a beaded filament preformaccording to a first embodiment of the present invention.

FIG. 6A illustrates a schematic view of the beaded filament preformaccording to the first embodiment of the present invention, having asingle sized bead positioned at a first spacing.

FIG. 6B illustrates a schematic view of the beaded filament preformaccording to the first 10 embodiment of the present invention, having alarger sized bead interspaced between a smaller sized bead.

FIG. 6C illustrates a schematic view of the beaded filament preformaccording to the first embodiment, having a larger sized beadinterspaced between a smaller sized bead, and positioned adjacentthereto.

FIG. 7A illustrates a schematic view of the beaded filament preformaccording to the first embodiment of the present invention, wherefilaments are horizontally arranged in a grouping typical of a laminatematerial.

FIG. 7B illustrates a schematic view of the beaded filament preformaccording to the first embodiment of the present invention, wherefilaments are diagonally arranged in a grouping typical of a laminatematerial.

FIG. 7C illustrates a schematic view of the beaded filament preformaccording to the first embodiment of the present invention, wherefilaments are horizontally arranged in a grouping typical of a laminatematerial, and where two different sized beads are used.

FIG. 7D illustrates a schematic view of the beaded filament preformaccording to the first embodiment of the present invention, similar toFIG. 7C, except the filaments are diagonally arranged.

FIG. 8 illustrates a schematic view of the beaded filament preformaccording to the first embodiment of the present invention, illustratingbeads of a filament prior to processing within a material having anoblong shape so that a properly shaped spherical void will be formed asa result.

FIG. 9 illustrates a cross-sectional view of an engineered materialmanufactured by assembling together a plurality of filaments accordingto the first embodiment of the present invention.

FIG. 10 illustrates a cross-sectional view of another engineeredmaterial manufactured by assembling together a plurality of filamentsaccording to the first embodiment of the present invention.

FIG. 11A illustrates a cylindrical tow using a filament preformaccording to the first embodiment of the present invention.

FIG. 11B illustrates a square-column tow using a filament preformaccording to the first embodiment of the present invention.

FIG. 12A illustrates a laminate manufactured by assembling a pluralityof tows as illustrated in FIG. 11A.

FIG. 12B illustrates a laminate manufactured by assembling a pluralityof tows as illustrated in FIG. 11B.

FIG. 13A illustrates a plurality of tows, as shown in FIG. 11A,assembled to form a fabric.

FIG. 13B illustrates a plurality of tows, as shown in FIG. 11B,assembled to form a fabric.

FIG. 13C illustrates a plurality of tows and laminates assembledtogether to form a fabric.

FIG. 13D illustrates a plurality of laminates.

FIG. 14 illustrates beaded filaments and mats aligned for processing toform a laminate/fabric.

FIG. 15 illustrates an first extrusion/spinning process formanufacturing the beaded filament preform according to the presentinvention.

FIG. 16 illustrates a second extrusion process for manufacturing thebeaded filament preform according to the present invention.

FIG. 17 illustrates a first extrusion process for manufacturing thebeaded mat preform according to the present invention.

FIG. 18 illustrates a second extrusion process for manufacturing thebeaded mat preform according to the present invention.

FIG. 19 illustrates a first extrusion process for manufacturing a towaccording to the present invention.

FIG. 20 illustrates a second extrusion process for manufacturing a towaccording to the present invention.

FIG. 21 illustrates a first extrusion process for manufacturing alaminate with the preform mat according to the present invention.

FIG. 22 illustrates a second extrusion process for manufacturing alaminate with the preform mat according to the present invention.

FIG. 23 illustrates a preform according to the present invention used toproduce a material using a continuous casting process.

FIGS. 24-25 illustrate a preform according to the present invention usedto produce a laminate or fabric using a pultrusion process.

FIG. 26 illustrates a texturized material according to a secondembodiment of the present invention with a first organization ofdimples.

FIG. 27 illustrates a texturized material according to a secondembodiment of the present invention with a second organization ofdimples.

FIG. 28 illustrates a texturized material according to a secondembodiment of the present invention with a third organization ofdimples.

FIG. 29 illustrates various structures capable of being manufacturedusing the preform materials according to the first and secondembodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Beaded Preforms as Precursors to Organized Voided Materials

A beaded preform according to the present invention is a precursorcomponent for incorporation into a material to form predeterminedsymmetrical or asymmetrical positioned or otherwise organized voids, orpores, to establish, for example, a material having organized vorasity.An example of such a material is a stress steering structure forresolving imposed loads primarily into compressive stress.Two-dimensional cross-sections of such three-dimensional stress steeringstructures are shown in FIGS. 1-4.

The preforms may be sacrificial (i.e., preliminary), permanent, or acombination thereof. In sacrificial preforms, the bead material whichforms the voids is eliminated at some point after incorporation into thebase material, generally during further processing. In permanentpreforms, the bead material remains in the voids, although it may bealtered or reformed in some way during processing.

The beads of the preforms may be of any shape and size required toproduce a desired engineered material, and may be hollow or solid, andany combination thereof. Generally, the beads are shaped such that theywill produce a void having a particular void volume and/or shape afterprocessing.

The beaded preforms are preferably made in one of two basic forms:filaments and mats, either of which may be rigid or flexible. Thesepreforms may be further assembled into tows and laminates by applying acoating to the filaments and mats, respectively.

A filament 2 preform according to the present invention is similar to astrand of beads (FIG. 5A) and comprises a strand 4 of spaced apart beads6 (FIG. 5B). The spacing may be asymmetrical, but is generally organizedand/or symmetrical, with a pattern of predetermined distances. Moreover,the beads may be equally sized, randomly sized, or (also) a repeatingpattern of particularly shaped beads as shown in FIGS. 6A-6C.

Mats 8 are two-dimensional arrays of assembled filaments 2 as shown inFIGS. 7A-7D, although they may be formed by assembling a plurality ofbeads in other ways to form a two-dimensional array. As shown in thefigures, vertical and horizontal spacing of the beads are generallyprovided in an organized, predetermined distance and pattern.

FIG. 8 illustrates a beaded filament having oblong shaped beads. Thebeads are formed in such shapes so that when incorporated into aparticular material, the voids, and thus the beads themselves ifpermanent, end up having a spherical shape after processing. Suchprocessing which benefits from these types of filaments may be a castingprocess, where high temperatures and/or compression rolling effect theshape of the preform, and thus, the shape of the void created whether ornot the preform is sacrificial or not.

Mats and filaments may be assembled to form a fabric, resulting in, forexample, material cross-sections illustrated in FIGS. 9-10 having voids12 and 14 (FIG. 9) and voids 16 (FIG. 10). As shown in FIG. 14, such afabric laminate may include alternating layers of mats 8 and filaments 2with a surface material 11 covering the top and bottom.

Tows 18 (FIGS. 11A-11B) are formed by coating a filament 2, generally,with a type of matrix material (e.g., thermosetting resin) 3. Similarly,laminates 20 are generally formed by coating a mat with a matrixmaterial, or may be manufactured by assembling a plurality of tows 2(FIGS. 12A-12B), or by coating an assemblage of a plurality of filamentsarranged in an array.

Tows and laminates, as well as filaments and mats, may also includecutting and positioning guides (e.g., recesses, protrusions), so thatthey may be easily cut, arranged and assembled for a particularapplication in intermediate and final product materials.

Intermediate and final products may be manufactured from composites 22of tows and laminates (FIGS. 13A-13D, and 14). For example, one way acomposite fabric may be made is by weaving, knitting, and otherwiseassembling together a plurality of tows, a plurality of laminates, or acombination thereof.

Composites, including fabrics, may be continuous (e.g., tapes) anddiscontinuous and may be manufactured for both intermediate materialsand finished products. For example, composites may be manufactured intoslabs, blooms, billets, panels, boards, and sheets (see FIG. 29).

One skilled in the art will appreciate that the void pattern of material(e.g., a stress steering structure) may be incorporated into a fabric byweaving, braiding, and knitting tows, such that the advantages of thisstructure are captured at two different levels. Moreover, the structureand material of the beads and coatings may be comprised of stresssteering structures (i.e., voided structures) such that, the advantagesof the stress steering structures are now captured at three levels.

Accordingly, there are numerous possible and potential matrices fortows, laminates, and fabrics for the present invention using metals,plastics, ceramics, and various alloys, mixtures and composites thereof.Alternative materials include semiconductors, textiles, paper, andbiomaterials.

A void created by a preform component may be used to house devices forintelligent materials for use in intelligent structures. Specifically,sensors, actuators, MEMS, and other devices may be incorporated within avoid of a structural element of a bridge, or a wing of an aircraft, forexample, to supply information regarding the performance of theelement/bridge or to induce an internal force on the structure to changeits shape or change a characteristic of the element (e.g., change theshape of the wing of an aircraft to create more lift). To incorporatesuch a device into an end product, the device may be used in place ofone or more of the beads in a filament or mat or incorporated in one ormore of the beads.

The preforms according to the present invention are produced usingconventional manufacturing processes. Accordingly, Applicant hasprovided a comprehensive list of manufacturing processes which may beused to manufacture the preforms according to the present invention,examples of which are illustrated in FIGS. 15-18. These include variouscasting, deformation, and forming processes for metals; blow molding,compression molding (cold/hot), transfer molding, cold molding,injection molding, reaction injection molding, thermoforming, rotationalmolding, and foam molding for plastics; pressure casting, slip casting,isostatic pressing, plasma spray forming, roll pressing, injectionmolding, and gelcasting for ceramics; and infiltration casting, filamentwinding, and isostatic pressing for composites.

One example of producing the novel preforms according to the presentinvention is shown in FIG. 15 and is described as follows.

Filaments: As shown in FIG. 15 and FIG. 16, filaments may be produced bya spinning process 31, in which extruded material is forced through adie 32 (spinneret) containing many small holes 34. The beads are addedthereafter by shape rolling 36, or preferably by inline drawing 38 andcalendaring operations on the filaments with embossed rollers 40.Drawing thins the filaments thereby increasing their tensile strength inanticipation of further processing. The finished filaments are gatheredon a take up spool 39. Filaments may also be produced by using rotaryextrusion as shown in FIG. 16.

Mats: Mats generally begin as extruded tape castings with beading addedinline by calendering with embossed rollers (as preferably done withfilaments) as shown in FIGS. 17-18. As shown, material is extruded outan extruder die 42 to produce a mat of material containing no beads.From there the 2D array enters into a calendering operation, which addsbeads with embossed rollers 40. However, beaded filaments may be used toform the mats by organizing a plurality of filaments into a mesh or byproperly aligning a plurality of filaments in an array with an extrudedmatrix material. The latter process is similar to continuous preformcasting (see below). The matrix material may include a reinforcementmaterial and may also be a composite.

Tows: Tows generally begin as beaded filaments and are generally formedinline in an extruding operation, for example, by coating filaments withan extruded matrix material as shown in FIGS. 19 and 20. Such processesare commonly used for wire and cable coating. The extruded coatingmaterial 43 is applied to a beaded filament 2 in a die body 44. Thefilament is introduced into the die body through a core tube 46. Aguider tip 48 aligns the beaded filament 2 within an opening 50 of a die52. Unconsolidated tows may then be superimposed (or otherwiseorganized) and fused, joined, or bonded inline to form other preformsand structures such as laminates and fabrics.

Laminates: Laminates generally begin as mats (or filaments/tows) and aregenerally formed inline in extruding operations as shown in FIGS. 21-22,for example, by coating mats with an extruded matrix material. Liketows, the coating material may also contain reinforcement material andmay also be another form of composite. The coating material may also beapplied in multiple layers, be functionally graded material, and beorganized in a hierarchical structure.

Like tows, unconsolidated laminates may be superimposed and fused orotherwise bonded to form composites, other preforms, and structures suchas fabrics. These combinations may be formed mechanically viainter-laminate connectors or mechanical fasteners (e.g., snap fits ortongues and grooves), or may be bonded via an adhesive, fusion bondingand welding (e.g., ultrasonic, microwave, rf welding, induction). It isworth noting that during the bonding process, sacrificial preforms aregenerally eliminated.

Plastic-matrix preform laminates may be melted slightly on theirsurfaces to achieve consolidation. In addition to being heated,superimposed metal-matrix preform laminates may be subjected tocompression rolling to enhance consolidation as well as the quality ofthe final product.

Laminates and fabrics according to the present invention may bemanufactured using the filaments and mats in, for example, a pultrusionprocess as shown in FIG. 24, a continuous casting process as shown inFIG. 23, and a continuous extrusion process as shown in FIG. 25.

Accordingly, all of the aforementioned processes to manufacture thepreforms according to the present invention may be continuous or batchprocesses and may be automated to produce continuous or discontinuouspreforms of high quality and uniformity.

Filaments, mats, tows, laminates, and fabrics according to the presentinvention may be used to create materials, including stress steeringmaterials, in a variety of additional manufacturing processes. Forconvenience, Applicant has provided the following list of manufacturingprocesses in which preforms according to the present invention may beused. These include:

-   -   Additive Manufacturing:        -   atomistic manufacturing;        -   layered manufacturing including fused deposition modeling,            stereo-lithography, optical fabrication, solid base (Ground)            curing, plasma spray forming, sputtering, vapor deposition;    -   Deformation and forming:        -   bulk deformation processes including impression-die forging,            open-die forging, coining, piercing, hubbing, fullering and            edging, roll forging, ring rolling, direct extrusion,            indirect extrusion, hydrostatic extrusion and impact            extrusion;        -   sheet metal forming processes including shearing, bulging,            rubber forming, high-energy-rate forming, superplastic            forming, deep drawing, embossing;        -   material removal including cutting, grinding, electrical            discharge machining, water-jet machining, abrasive-jet            machining, chemical machining and electrochemical machining            and grinding;    -   Casting:        -   permanent molds including slush casting, pressure casting,            insert molding, centrifugal casting and infiltration            casting;        -   expendable molds including vacuum casting, ceramic-mold            casting, plaster-mold casting, shell-mold casting and sand            casting;        -   gel-casting, injection molding, compression molding,            transfer molding, insert molding;    -   Particulate material processing;        -   sintering, cold isostatic pressing, and hot isostatic            pressing; and    -   Assembly and joining processes;        -   friction stir welding, Resistance welding, explosive            welding, brazing and soldering, arc welding, and laser            welding.

The following example addresses the use of preforms as used withcontinuous manufacturing processes.

Continuous Manufacturing Processes Utilizing Preforms—Continuous Casting

The preforms according to the present invention are ideally suited forproducing engineered materials using a continuous material manufacturingprocess, i.e., continuous (preform) casting and continuous extrusionmanufacturing processes. Continuous preform casting utilizes two longestablished manufacturing processes used for casting a continuous tapeof material—pultrusion and continuous casting.

Conventionally, these manufacturing processes produce materials having aconstant cross-section with shapes including round, rectangular,tabular, plate, sheet, and structural products. In the presentinvention, the processes are modified to include preform fixtures forchanneling filaments and/or mats into proper alignment with a matrixmaterial (and optional continuous, reinforcement such as fibers). Thefixtures may also be used to contour the preform/matrix combination.

The production flow in continuous preform casting may be uninterruptedfrom the introduction of the preforms into a molten material to theoutput of engineered products. Whatever the primary material (metal,plastic, or ceramic), the initial feedstock is a fluid (or a melt):molten metals, monomer solutions, slips, and slurries. Post castingprocesses vary depending on the choice of the matrix material, withceramics being sintered and metals being generally rolled.

The following is an example of a continuous casting process. In thecontinuous casting process, for example, as illustrated in FIG. 23, acontinuous mat 8 (and/or filament) is fed into a tundish 60 of a castingapparatus 57 where molten material 59 and the mat flow out of thetundish through a water-cooled, continuous mold 62. The mold generallydetermines the thickness and/or profile of the resulting material, butnot the length, and may be positioned vertically, horizontally or atanother angle, depending on the desired material flow.

There, the mat/material composition flows down a discharge rack 63 andis cooled. The cast can be further processed into final form, throughvarious inline applications of heat and mechanical force (e.g., pinchrolling 64, reheating 66) to give it the desired shape, size, physicalproperties, and surface qualities. Such inline applications includepinch rolling, reheating/cooling, and the like. After such processing, asizing area 67 sizes the slab of material to a particular size, wherebya cut-off torch 65 (or other cutting device appropriate for theparticular cast material) is used to cut the slab into a plurality ofpieces.

Due to the potential rigors of both the casting (e.g., temperature) andpost-casting processing (e.g., rolling), the size, shape, alignment, andcomposition of the beaded preforms according to the present inventionfor inclusion in such a casting process may be structured and organizedin anticipation of alterations resulting from the process to achieve thedesired array of voids in the final product. To that end, it ispreferable that characteristics of the preforms substantially match withthe mechanics of the continuous processing process to produce thedesired product.

While the preforms can be organized for extreme (or bulk) deformationprocesses, these are equally well suited for near net shape casting, orthin-slab casting, for example.

Although metals are known materials which are used in a continuouscasting process, continuous casting of plastics and ceramics can beachieved through a variation of the basic tape casting process. Forexample, a liquid resin material (usually acrylic syrup) is pouredbetween two horizontal and continuous belts separated by a gasket. Thegasket retains the liquid resin and defines the thickness of the tape. Asimilar process may be used to produce metal and ceramic tapes, as wellas combination tapes that are a mix or alloy of all three types of basicmaterials, i.e., metals, plastics, and ceramics. Laminates and fabricsaccording to the present invention may be easily manufactured using thisprocess by using a preform fixture to supplement, or in place of, thegasket.

Preforms according to the present invention may also be fabricated asexpendable patterns in mold casting. A pattern, or copy, in one piece orin sections, of a product to be made by casting is used to establish theshape and dimensions of the mold cavity. While the matrix materials ofpatterns are expendable, these patterns contain the beaded preformsaccording to the present invention (that may be either sacrificial orpermanent). Among the casting processes that may use expendable preformpatterns are lost foam and investment casting as explained below.

In conventional lost foam casting, the pattern is made of expendablepolystyrene (EPS) beads. As the molten metal is poured into the mold, itreplaces the EPS pattern, which vaporizes. The Preforms, withpolystyrene (PS) matrices with incorporated beaded filaments and/ormats, may be used in this process to form engineered products. Thesepatterns may begin as PS preform slabs.

PS preform slabs may be made by continuous preform casting or continuousextrusion processes using a PS solution as feedstock. The slabs may beformed by introducing a foaming agent into a PS solution, or melt, thatthen is properly integrated with beaded filaments and/or mats to form acontinuous tape. The tape may pass between belts or plates with aspecific gap between them while the foaming agent expands the tape tofill the gap, fixing the dimensions of the tape. This PS continuous tapemay be cooled and cut into the slabs. The slabs may be partially orfully expanded, depending on the choice of subsequent castingprocedures.

The beaded filaments and/or mats are aligned in the PS solution or meltto reconcile the degree of expansion with the geometry of the void arraydesired in the final product.

For high-production runs, slabs may be converted into EPS preformpatterns in heated molds or dies that burn away excess material from theslabs to conform each one to the shape of the desired pattern. Forexample, a slab can be expanded within a heated mold to conform to theshape of the mold cavity, or an oversized slab can be forged in a heateddie to the desired shape. For shorter runs, pattern shapes may be cutout of the slabs using conventional woodworking equipment and, ifnecessary, these shapes may be assembled with glue to form the finalpattern.

Squeeze Casting is a combination of casting and forging. In thisprocess, forging means squeezing, or pressing, an unconsolidatedfeedstock into a predetermined shape. In squeeze casting, castingpreform feedstock according to the present invention is placed in thebottom section of a preheated die. A heated upper die then descends,applying pressure throughout the duration of consolidation of thefeedstock. Using this process, intricate shapes can be produced atpressures that are far less than would normally be required for hot orcold forging. Accordingly, tows and laminates can be consolidated by theheat and pressure and shaped by the die to form the final product, whilethe void space created by the beaded preforms can be preserved (althoughthese preforms may be sacrificed in the process).

This thermo-mechanical processing of the casting feedstock duringsqueezing produces a forged microstructure that has enhanced ductilityover the original cast microstructure. In a similar embodiment of thisprocess, a liquid (or thixotropic material) is forced around a preformpattern(s) in a mold. Thixotropic materials eliminate the need tointroduce a precise amount of molten metal into the die since chunks ofsolid matrix material are used and these have been heated into asemi-solid (liquid plus solid) state.

Because of the properties of the thixotropic material, it can be handledmechanically, like a solid, but shaped at low pressures because it flowslike a liquid when agitated or squeezed. An additional advantage of thematerial is that the absence of a turbulent flow minimizes gas pickupand entrapment. Moreover, since the material is already partially solid,solidification shrinkage and related undesirable porosity is reduced.For example, semi-solid metal flows in a viscous manner, allowingthin-cast sections to be filled rapidly without jetting and spraying ofliquid metal that would normally occur.

Pultrusion

Although the continuous preform casting process may be used to formintermediate and final products composed of plastics, metals, andceramics, plastic resins are typically the matrix material used inpultrusion. Pultrusion is a cost-effective automated process forcontinuous production of composite materials of constant cross-sectionalarea such as round, rectangular, tabular, plate, sheet, and structuralproducts. Recent innovations, however, have also allowed pultrusionfabrication of composites with varying cross-sectional areas.

Pultrusion may be used to manufacture both laminates and fabricscontaining the preforms according to the present invention (FIG. 24).Accordingly, fixtures 73 are provided in a pultrusion system to properlyalign the preforms with the matrix material consistent with the profileand architecture of the desired product.

In the present invention, pultrusion, as shown in FIGS. 24-25 generallyincludes a fiber delivery system 69, a resin bath 74, preformfixtures/heated die 76, synchronized pullers 78, and a cut-off device 80(e.g., torch, saw, and the like). One or more bundles of continuousfilaments 2 (or mats, and/or weaves) are guided through deliveryfixtures 73 that align the preforms with a matrix material and contourthe combination of components into a desired shape. The composition maythen be pulled through one or more heated dies 76 (fixed or floating)for further shaping, compacting, and solidifying of the matrix materialand for eliminating sacrificial filaments, mats, and/or weaves.Thereafter, the fabricated material is cooled and cut to length forfurther fabrication into intermediate and finished products.

Continuous Extrusion

Continuous Extrusion may be used in coordination with pultrusion(extruding apparatus 31 as shown in FIG. 25) to yield a continuousprocess whereby preforms are created through extrusion, and organizedinto final products using pultrusion. Extrusion (as previouslydescribed) is a process that forces a continuous stream of material intoa shaping tool (a die), or into some other subsequent shaping process,to form a filament, mat, and laminate according to the presentinvention.

Accordingly, laminates may be formed through either post extrusioncoating of beaded filaments and mats with a matrix material, or postextrusion addition of texture to a tape. In the latter case, the tapemay be either texturized with patterns that are applied by (for example)calendering, or excised through (for example) selective laser burnout.

Batch Processing

Batch processing technologies also may be used to fabricate preformsaccording to the present invention, as well as engineered intermediategoods and consumer products including those having a stress steeringstructure. Such batch processes include additive manufacturing (AM) andparticulate manufacturing technology. The former is solely a batchprocess, while the latter may also be a continuous process.

AM provides the capability to incorporate actual voids, versus voidprecursors, into fabrics in a one-step process. Additive Manufacturingis a family of processes that involve creating 3D objects byautomatically placing 2D layers of material on top of each other undercomputer control. The advantage is that a structure's geometriccomplexity has little impact on the fabrication process. Within thisfamily are processes currently known as Rapid Prototyping and SolidFreeform Fabrication, or Layered Manufacturing, among others. Theseinclude purely additive processes, such as Selective Laser Sintering andLaser Metal Deposition, and hybrid methods like Shape DepositionManufacturing, which involves both material deposition and removaloperations.

AM processes reproduce preforms layer-by-layer in an uninterruptedsequence. For example, a fabric according to the present invention maybe produced as a series of alternating layers of solid mass and layerscontaining either beads (sacrificial or permanent) or actual voids.

An attractive and powerful feature of AM as used in conjunction with thepresent invention is the capability to endow products with varyingmacro- and microstructures. Accordingly, this technology may be employedto incorporate actual voids and preform materials in fabrics, and tomake heterogeneous and hierarchical compositions.

AM technology utilizing 3D printing may also be used which brings thepotential for production of intermediate and finished fabrics accordingto the present invention to create functional parts and products madeout of plastic, metal, and ceramic powders.

Particulate manufacturing technology (Powder Metallurgy) is a process bywhich fine powdered materials (metals, plastics, and ceramics, amongothers) are blended, pressed into a desired shape (compacted), and thenheated (sintered) in a controlled atmosphere to bond the contactingsurfaces of the particles and establish the desired properties. Properlysized, shaped, and positioned, filaments and mats according to thepresent invention may be incorporated in this process by surrounding thepreforms with powdered material and compacting this composition into a“green” fabric for later sintering into a final engineered product. Oneadvantage of this process is the ability of the assembled material tokeep its shape before and during sintering. During sintering, the“green” fabric may be heated just below the melting point of the matrixmaterial, right below its liquid melt point. Consequently, the compactwould not loose its shape. Thus, the void space would be preservedbecause the compacted particles would melt only slightly and bond toform the final product. During sintering, of course, any sacrificialpreforms may be eliminated.

For high tolerance products, the sintered product may be re-pressed,which in general may make the product more accurate with a bettersurface finish. The voids also may be impregnated, for example, in anoil bath. This process is very similar to continuous casting asdescribed above, except that the matrix material is a powder, not amelt.

Particulate technology may be used to form fabrics to be used asexpendable patterns for lost foam and investment casting, as well aspreforms for squeeze casting. Particle technology, of course, is thebasis of various ceramic and polymer resin processing techniques,including tape casting of ceramics and plastics.

The symmetry of a particular stress steering structure and theconcomitant orthogonal alignment of the voids afford the manufacture ofengineered materials, components, products, and structures using a widerange of manufacturing processes set out below. Which of these processesis best for manufacturing a particular product is a function of severalbasic considerations including product geometry, materialcharacteristics, and economics.

Texturized Materials as Precursors to Voided Stress-Steering Structures

The voids for engineered structures, including stress steeringstructures, may also be provided by incorporating a texture onto alaminate. Examples of such textures are illustrated in FIGS. 26-28. Asshown, dimples 78 are imparted onto a surface of a material. Suchdimples may be involve the entire thickness of the material, in that,dimples are present on one side (i.e., shallow openings), andcorresponding protruding areas on the other side of the material.

Generally, to produce preferred symmetrical voids according to thepresent invention using texturizing, a pattern of texture may beincorporated into one or both surfaces of a laminate, depending on thevoid array to be realized in the final engineered product. Texturizingmay also impart tape cutting and laminate stacking guides so that thelaminates may be assembled into a composite and final products moreeasily (as with tows and laminate detailed above).

Textures may be added to laminates through imprinting and excising(i.e., the removal of material). To minimize material requirements,imprinting is used to impart a required texture according to the presentinvention on a laminate surface. Imprinting redistributes the materialof the laminate, so the material is not wasted (as it is throughexcising). Accordingly, void precursors in laminate surfaces may be theresult of (1) localized material compression which redistributesmaterial out-of-plane (e.g., forged indentures), or (2) redistributionof the material of the laminate in-plane (e.g. by shape rolling).

In a preferred embodiment, a thixotropic laminate material is usedduring the imprinting of the texture. The laminate is imprinted when thelaminar material is heated to a “green” state so that the materialeasily redistributes itself. In a continuous casting or molding process,this is readily accomplished in situ during the casting of metal,plastic, and ceramics. Thus, metals like aluminum and steel (e.g.,foils) could be imprinted inline at the end of a hot rolling sequence;plastics could be imprinted inline, for example, during plastic filmcasting; and ceramics could be imprinted inline during tape casting whenthe tape is in a green, unfired state.

Assuring material redistribution, of course, is not a concern whenexcising laminates to create the textured patterns through, for example,selective laser burnout or chemical etching.

An advantage of texturizing tape castings to produce patterned laminatesis the ability to consolidate tapes using heat, pressure, and dwell timeto form a monolithic composite structure comprising many layers (whichmay be of different base compositions to produce functionally-gradedproducts, for example). This advantage may be enhanced by drawing andtexturizing the unconsolidated tapes as a continuation of the tapecasting line while the tapes are still heated.

Composites formed of textured laminates are generally preferably formedusing mechanical and adhesive joining as well as welding. This isespecially true of texturized metals, although metals may be heated andcompressed to achieve consolidation. Texturized ceramic laminates, onthe other hand, must be sintered.

Texturized plastic laminates may be welded, as well, using microwave,ultrasonic, rf, and induction techniques. Induction welding uses theheat generated by a metal filler in the plastic moving through amagnetic field to heat the plastic material.

While the system of the present invention has been described withreference to the above manufacturing materials, processes, and systems,it should be apparent to those skilled in the art that the presentinvention may be used/made with other materials, processes, and systemsnot specifically referenced here.

Having described the invention with reference to the presently preferredembodiments, it should be understood that numerous changes inconstruction may be introduced without departing from the true spirit ofthe invention as defined in the appended claims.

1. A method for manufacturing a beaded preform for forming a pluralityof voids in an engineered material comprising: extruding a preformmaterial out a first opening to produce an extruded preform material;calendering said extruded preform material to form a beaded filamentpreform comprising a plurality of beads spaced apart and connected byone or more filaments along said extruded preform material; introducingthe extruded preform material into an amorphous first material to coatthe beaded preform material such that the first material has an internalsurface that is reciprocal to the shape of the extruded preformmaterial; and shaping the coated beaded preform material into apredetermined form and consolidating the form to produce an engineeredmaterial configured internally as a lattice having an internal surfacethat is reciprocal to the shape of said extruded beaded preformmaterial, whereby the beaded preform forms a plurality of voids in theengineered material.
 2. The method of claim 1, wherein at least one ofsaid beads is solid and comprises the extruded preform material.
 3. Themethod of claim 1, wherein at least one of said beads is hollow.
 4. Themethod of claim 1, wherein at least one of said beads comprises amaterial which includes a modulus of elasticity which is less than amodulus of elasticity of the amorphous material.
 5. The method of claim1, wherein the calendering step includes the step of embossing saidextruded preform material via one or more calendering operations.
 6. Themethod according to claim 5, wherein prior to embossing said extrudedpreform material, said method includes the step of drawing said extrudedmaterial to produce a drawn material oriented for said embossing.
 7. Themethod according to claim 5, wherein said method produces a filamentcomprising a strand of said beads arranged in a symmetrical patternabout the long axis of said strand.
 8. The method according to claim 5,wherein said method produces a two-dimensional array of said beadsarranged in a symmetrical pattern about an axis of said two-dimensionalarray.
 9. The method of claim 5, wherein at least one of said beads issolid and comprises the extruded preform material.
 10. The method ofclaim 5, wherein said embossing comprises squeezing portions of theextruded preform material so as to create said plurality of beads suchthat the density of said extruded preform material is varied.
 11. Themethod of claim 5, wherein said embossing comprises compressingcorresponding portions of both opposing sides of the extruded preformmaterial toward a central portion of the extruded preform material toform a plurality of beads spaced apart along said extruded preformmaterial such that the density of said extruded preform material isvaried.
 12. The method of claim 5, wherein said embossing comprisescompressing corresponding portions of the extruded preform materialabout an axis so as to create a plurality of beads spaced apart alongsaid extruded preform material such that the density of said extrudedpreform material is varied.
 13. The method of claim 5, wherein saidembossing comprises compressing portions of the extruded performmaterial about an axis such that the density of said extruded preformmaterial is varied.
 14. The method of claim 5, wherein said embossingdensifies portions of the extruded preform material to form saidplurality of beads spaced apart along said extruded preform material,such that the density of said extruded preform material is varied. 15.The method of claim 5, wherein said embossing comprises densifyingportions of the extruded preform material to a greater extent thananother portion of said extruded preform material such that the densityof said extruded preform material is varied.
 16. The method of claim 5,wherein said embossing alters a microstructure of a portion of theextruded preform material such that said microstructure of said extrudedpreform material is varied.
 17. The method of claim 5, wherein saidembossing moves or removes an imperfection in a portion of said extrudedpreform material such that a property of said extruded preform materialis varied.
 18. The method of claim 5, wherein, subsequent to saidembossing, a portion of said plurality of spaced apart beads are lessdense than another portion of the extruded preform material such thatthe density of said extruded preform material is varied.
 19. The methodaccording to claim 5, wherein said embossing alters a mechanicalproperty of a portion of said extruded preform material such that saidmechanical property of said extruded preform material is varied.
 20. Amethod for manufacturing a beaded preform for forming a plurality ofvoids in an engineered material comprising: extruding a preform materialout a first opening to produce an extruded preform material; embossingsaid extruded preform material to form a beaded filament preformcomprising a plurality of beads spaced apart and connected by one ormore filaments along said extruded preform material; solidifying theextruded preform material to form a beaded preform material; introducingsaid beaded preform material into an amorphous first material to coatthe beaded preform material such that the first material has an internalsurface that is reciprocal to the shape of the beaded preform material;and shaping the coated beaded preform material into a predetermined formand consolidating the form to produce an engineered material, wherebythe beaded preform forms a plurality of voids in the engineeredmaterial.
 21. The method of claim 20, wherein said consolidating stepcauses an internal surface of the first material to be complementary tothe shape of said beaded preform material.
 22. The method of claim 20,wherein the introducing step comprises guiding said amorphous firstmaterial into a space having a predetermined size wherein the firstmaterial is induced by mechanical action to cause an internal surface ofthe first material to take on a shape complementary to the shape of saidbeaded preform material.
 23. The method of claim 20, wherein said beadedpreform material comprises a strand wherein the long axis of said strandintersects the beads spaced apart thereon.
 24. The method of claim 20,wherein: said consolidating step unifies said first material into acompact mass configured internally as a lattice having an internalsurface that is reciprocal to the shape of said beaded preform material;and said consolidation alters a microstructure of a portion of saidcompact mass such that said microstructure of said compact mass isvaried.
 25. The method of claim 20, wherein a portion of the beadedpreform material in the consolidated form is not collinear with the longaxis of the consolidated first material in the consolidated form, andwherein an internal surface of the consolidated first material isreciprocal to the shape of said beaded preform material.
 26. The methodof claim 20, wherein at least one of said beads is solid and comprisesthe extruded preform material.
 27. The method of claim 20, wherein atleast one of said beads is hollow.
 28. The method of claim 20, whereinat least one of said beads comprises a material which includes a modulusof elasticity which is less than a modulus of elasticity of theamorphous material.